The present invention relates generally to an apparatus for housing an electronic circuit and providing a means for connecting external inputs and outputs to that circuit. It is particularly suited, however, for housing an electronic ice control device used to maintain water or other liquids at a freezing temperature.
Cooling apparatus used for cooling beverages to a desired temperature typically circulate the beverage through coils immersed in water or other liquid which is kept at a freezing temperature. Some portion of the water or other liquid is allowed to freeze to a solid form in order to provide a heat sink for cooling the beverage. The frozen liquid is referred to as an ice bank.
Ice bank control devices utilize means for sensing the presence of ice and controlling the operation of a cooling apparatus accordingly. An ice bank is thereby allowed to grow to a predetermined size. Conventional ice bank control devices have generally been of the mechanical type. These devices use a capillary tube containing a solution which freezes when the tube is surrounded by ice. The expanding frozen solution within the capillary tube then compresses a diaphragm which operates an electrical switch. The electrical switch serves to turn a cooling compressor on or off and, thereby, controls the extent of ice formation.
More modern ice bank control devices, however, utilize electronic sensing means to determine the presence of ice. These devices utilize electrodes to carry current into the liquid and thence to ground. When a liquid undergoes a phase transformation into the solid form, its electrical resistance increases. If a constant current source is used to feed current to the sensing electrode, the presence or absence of ice surrounding the electrode may be detected by measuring the potential drop to ground at the electrode. Other electronic means can then be used to switch power on or off to the cooling compressor.
Electronic ice bank control devices present a number of advantages over their mechanical counterparts including lower cost and greater reliability. Also, since electronic devices measure the phase change directly rather than indirectly by measuring temperature, their operation is not affected by changes in the freezing point of the water caused by the addition of solutes.
Therefore, with the advent of electronic ice bank control devices, there has developed a need for a specialized packaging and connecting apparatus. It is an object of the present invention to provide a housing for the electronic control circuitry which will serve to protect the electronic components and electrically conductive surfaces from contact with water.
It is a further object of the present invention to provide a means for easily removing and replacing a printed circuit board upon which the elements of the electronic control circuit are mounted. As all electronic components are destined to fail at some time or other, it is desirable that removal and replacement be accomplished with a minimum of time and effort in order to lower service costs. Much time and effort can be saved by minimizing the number of electrical and mechanical connections which must be severed before the electronic circuitry can be removed. Accordingly, it is an object of the present invention to provide a connecting means for the printed circuit board containing the electronic circuitry which allows the removal of the printed circuit board without affecting power or sensor connections.
It is a still further object of the present invention to provide a means integral to the housing which allows the state of the final control output of the electronic circuitry to be observed. The final control output is invariably a contact closure, and it is desirable for the state of the contact to be observable without removing the housing or using a voltmeter at the output terminals. For example, when servicing the entire cooling apparatus, it is necessary to determine if the electronic control circuitry is operating properly independent of the operation of the compressor.